1,2-bis{8 3-alkyl-4-hydroxy-5-(dialkylaminomethyl-phenylthis{9 ethanes

ABSTRACT

This invention is directed to a new series of compounds which are useful as antioxidants. These compounds are represented by the formula: WHEREIN R1 is selected from the group consisting of alkyl groups of up to 12 carbon atoms, cycloalkyl groups of from about six to eight carbon atoms and aralkyl groups of from about seven to nine carbon atoms, R2 and R3 are selected from the group consisting of hydrogen and methyl, R4 and R5 are selected from the group consisting of alkyl groups of up to five carbon atoms and X is a diradical containing from about two to about 14 carbon atoms and is selected from the group consisting of: A. POLYMETHYLENE DIRADICALS OF THE FORMULA -(CH2)n-wherein n is a whole number from 2 to 14; B. BRANCHED CHAIN POLYALKYLENE DIRADICALS OF THE FORMULA: WHEREIN N IS A WHOLE NUMBER FROM 0 TO 11 AND THE R groups may be hydrogen or alkyl groups and at least one of the R groups is an alkyl group.

[151 3,686,313 Aug. 22, 1972 l,2-BIS[3-ALKYL-4-HYDROXY-5-(DIALKYLAMINOMETHYL- PHENYLTHIS1ETHANES [72] Inventor: Francis X. OShea,

Conn.

[73] Assignee: Uniroyal, Inc., New York, NY. [22] Filed: Nov. 29, 1968[2]] Appl. No.: 780,237

Naugatuck,

[52] US. Cl. ..260/570.9, 252/47, 252/402, 260/45.9 R, 260/247.7 R,260/294.7,

Primary Examiner-Robert V. Hines Att0rneyWillard R. Sprowls 5 7 ABSTRACTThis invention is directed to a new series of compounds which are usefulas antioxidants. These compounds are represented by the formula:

wherein R is selected from the group consisting of alkyl groups of up to12 carbon atoms, cycloalkyl groups of from about six to eight carbonatoms and aralkyl groups of from about seven to nine carbon atoms, R andR are selected from the group consisting of hydrogen and methyl, R and Rare selected from the group consisting of alkyl groups of up to fivecarbon atoms and X is a diradical containing from about two to about l4carbon atoms and is selected from the group consisting of:

a. polymethylene diradicals of the formula (Cl-l wherein n is a wholenumber from 2 to 14; b. branched chain polyalkylene diradicals of theformula:

wherein n is a whole number from 0 to 1 l and the R groups may behydrogen or alkyl groups and at least one of the R groups is an alkylgroup.

3 Claims, N0 Drawings 1 ,2-BIS[ 3-ALKYL-4-HYDROXY-5-(DIALKYLAMINOMETHYL- PHENYLTHISlETl-IANES This invention relates to anew series of compounds which are useful as antioxidants for rubber,plastics, fats, petroleum products and other organic materials normallysubject to oxidative deterioration. The compounds of this invention maybe represented by the forwherein R may be an alkyl group of up to 12carbon atoms, a cycloalkyl group of from about six to eight carbon atomsor an aralkyl group of from about seven to nine carbon atoms, R and Rare selected from the group consisting of hydrogen and methyl, R and Rare selected from the group consisting of alkyl groups of up to fivecarbon atoms or R and R may be joined to form with the nitrogen atom, aradical selected from the group consisting of morpholinyl, pyrrolidinyland piperidinyl, and X is a diradical containing from about two to about14 carbon atoms and is selected from the group consisting of:

a. polymethylene diradicals of the formula (CH wherein n is a wholenumber from 2 to 14, for example:

CH CI-l and -(CH b. branched chain polyalkylene diradicals of the for-CH CH c. aralkyl diradicals of the formula:

atoms and n is a whole number from to 4, for example:

CH CH3 0 wherein R is an alkyl group of one to four carbon 6 e. aralkyldiradicals of the formulas:

on, s ell-.-

f. cyclic hydrocarbon containing diradicals of the general formula:

wherein R may be hydrogenor an alkyl group and n is a whole number from0 to 6, for example:

g. aliphatic diradicals containing hetero atoms of the general formula:

wherein R may be hydrogen or alkyl, n is a whole number from 1 to 6 andZ is selected from the group consisting of O, S-, SO and NR'- (wherein Ris an alkyl group), for example, Cl-I CH OCl-l Cl-l and CH,CH SCH CH h.diradicals of the formulas: CH CH OCH CH O CHgCHz and i. aralkyldiradicals of the general formula:

o Iii-(l)- R wherein R may be hydrogen or an alkyl group, for example:

CH3 H3 C113 CH3 l I I l CH3 CH Our invention is also concerned with anovel method of preparing the aforementioned compounds. This methodinvolves the reaction of 1 molar equivalent of the compound of thegeneral formula:

in which R,, R R and X are as previously described with two molarequivalents of formaldehyde and two molar equivalents of a dialkylamineof the formula:

in which R,, R and R are as previously described with two molarequivalents of an alkali metal hydroxide and one molar equivalent of anorganic dihalide of the formula:

Hal X Hal in which Hal represents a halogen atom and X is as previouslydescribed.

The reaction used to prepare intermediate A may be carried out in asuitable water miscible solvent such as methanol, ethanol, isopropanol,dioxane, ethylene glycol dimethyl ether, etc. at a temperature fromabout room temperature to about 100 C.

Preferred solvents for the reaction are methanol, ethanol andisopropanol, while the preferred temperature is in the range of 50 C. to100 C. The reaction is ordinarily carried out at or near the refluxtemperature of the solution, a preferred reaction time of up to 4 hoursis advisable. Longer times may be used, however they are not necessary,as the reaction is generally completed within 30 minutes.

The reaction may also be carried out in a two-phase system such asbenzene-water, xylene-water, etc. using vigorous agitation. Althoughlonger reaction times are generally employed than in homogenoussolution, this heterogeneous system has the advantage of providing asimplified recovery procedure. In such a two-phase system, the productis soluble in the organic phase which can be readily separated from theaqueous phase containing the alkali metal halide. The product is thenobtained by removing the solvent from the organic phase.

Method B This method involves the reaction of two molar equivalents of amercaptophenol of the formula described in Method A, with one molarequivalent of a non-conjugated diolefin of from five to 30 carbon atoms,under acid catalysis.

This reaction may be carried out without a solvent or in a non-polarorganic solvent such as hexane, benzene, xylene, etc. at a temperatureup to about C. The acid catalyst which may be employed includes mineralacids such as sulfuric acid, Lewis acids such as AlCl and BF;,, andheterogenous catalysts such as acid clays and acidic ion exchangeresins.

The mercaptophenols which may be used to prepare these intermediates byeither Method A or Method B include:

2-methyl-4-mercaptophenol,

2-isopropylA-mercaptophenol,

2-t-butyl-4-mercaptophenol, 2-octyl-4-mercaptophenol,

Z-(a-methylundecyl)-4-mercaptophenol,

2-cyclohexyl-Lmercaptophenol,

2-cyclooctyl-4-mercaptophenol, 2-(a-methylbenzyl)-4-mercaptophenol,2,5-dimethyl-4-mercaptophenol, 2-t-butyl-4-mercapto-5-methylphenol,2-t-octyl 4-mercapto5-methylphenol, 2-dodecyl-4-mercapto-5-methylphenol,2-cyclooctyl-4-mercaptoS-methylphenol, 2,3,5-trimethyl-4-mercaptophenol,2-t-butyl-3,5-dimethyl-4-mercaptophenol,2-dodecyl-3,5-dimethyl-4-mercaptophenol,2-cyclohexyl-3,5-dimethyl-4-mercaptophenol and2-benzyl-3,5-dimethyl-4-mercaptophenol.

Some of the diolefins which may be used include:

Para-diisopropenyl benzene,

Meta-diisopropenyl benzene,

Divinyl benzene,

Vinyl isopropenyl benzene,

l ,7-Octadiene,

Vinyl cyclohexene,

1-Methyl-4-isopropenyl cyclohexenel l-4-hexadiene,

l ,1 3-Tetradecadiene 2,7-dimethyl- 1 ,7 -octadiene,

Ethylidene norbornene and Isopropylidene norbornene.

The novel compounds disclosed herein have previously been unreported,and such compounds are set forth for the first time. In US. Pat. No.2,472,318, issued June '7, 1949 to Philip Subkow, compounds of thefollowing formula were disclosed:

wherein R is selected from the group consisting of an aryl, alkylaryl,substituted aryl, alkylaryl groups, S is sulfur and R is a low molecularweight alkyl group. These compounds are disclosed as possessing activityas oxidation inhibitors for lubricating oils. Among the possiblestructures set forth by Subkow was included the following compound,which is considered the closest prior art uncovered:

CH3 CH3 My contribution differs from the prior art in that the hydroxylgroup in my compounds is para to the sulfur atom rather than ortho andmy compounds contain a dialkylaminomethyl group ortho to the phenolichydroxyl. The presence of this group provides these compounds withunexpected properties as a nondiscoloring antioxidant. Chief among theseproperties is a striking advantage in color over compounds related tothe prior art compound which do not contain such a dialkylaminomethylgroup. This color advantage is of considerable commercial importance.

To illustrate the novel bis-phenolic compounds and their methods ofpreparation, the following examples are given. It should be understood,however, that these examples are merely illustrative and are not to beregarded as limitations to the appended claims since the basic teachingsthereof may be varied at will, as will be understood by one skilled inthe art. In the examples, the proportions are expressed in parts byweight unless otherwise noted.

EXAMPLE 1 The preparation of 1,2-bis[3-methyl-4-hydroxy-5-(dimethylarninomethyl)-phenylthio]ethane.

To a solution of 28 g. (0.2 mole) of 2-methyl-4-mercaptophenol and 16 g.(0.2 mole) of 50 percent aqueous sodium hydroxide in 150 ml. of ethanolwas added g. (0.1 mole) of ethylene dichloride. The solution was heatedgently for 10 minutes near reflux. The solution was then cooled andpoured into water. The oil which separated was extracted with ether andthe ether extract was dried with anhydrous sodium sulfate and evaporateddown to an oil which crystallized. The product was triturated with abenzene-hexane mixture and filtered yielding 24.5 g. (80 percent) ofl,2-bis(3- methyl-4-hydroxyphenylthio)ethane, m.p. 93-96. The meltingpoint was raised to 96-98 by recrystallization from benzene.

To a solution of 30.6 g. (0.1 mole) of 1,2-bis(3-methyl-4-hydroxyphenylthio)ethane and 50 g. (0.22 mole) of 45 percentaqueous dimethylamine in ethanol was added 18 g. 0.22 mole) of 37percent aqueous formaldehyde. The solution was then heated slowly toreflux and refluxed for 3 hours. The solution was then cooled and acrystalline precipitate formed. It was filtered ofi, washed with aqueousethanol and dried to give 37 g. (88 percent yield) of1,2-bis[3-methy1-4- hydroxy-S-(dimethylaminomethyl)phenylthio]-ethane,m.p. 93-95 C after recrystallization from hexane.

Analysis: Calcd. for C H N O S C, 62.85; H, 7.62; N, 6.67; S, 15.23.

Found: C, 63.02; H, 7.81; N, 6.35; S, 15.51.

EXAMPLE 2 The preparation of 1,2-bis[3-t-butyl-4-hydroxy-5-(dimethylaminomethyl)phenylthio ethane.

1 ,2-Bis( 3-t-butyl-4-hydroxyphenylthio)ethane, m.p. 121123 C, wasprepared by reacting 2-t-buty1-4- mercaptophenol with ethylenedichloride in the same manner as described in Example 1.

This intermediate was then reacted with formaldehyde and dimethylaminein the same manner as described in Example 1 to yield1,2-bis[3-t-butyl-4 hydroxy-5-(dimethylaminomethyl)phenylthio] ethane,m.p. 133-135 C is crystallization from ethanol.

Analysis: Calcd. for C H N O S N, 5.56; S, 12.70.

Found: N, 5.79; S, 13.0.

EXAMPLE 3 The preparation of 1,4-bis[3-t-butyl-4hydroxy-5-(dimethylaminomethyl)phenylthio butane.

1 ,4-Bis( 3-tbuty1-4-hydroxyphenylthio)butane was prepared by reacting2-t-butyl-4-mercaptophenol with 1,4-dichlorobutane in the same manner asdescribed in Example 1.

This intermediate was then reacted with formaldehyde and dimethylaminein the same manner as described in Example 1 to yield1,4-bis[3-t-butyl-4- hydroxy-S-(dimethyl-aminomethyl)phenylthio] butanein percent yield, m.p. 129-130 C.

Analysis: Calcd. for C H N O S C, 67.6; H, 9.02; N, 5.26; S, 12.03.

Found: C, 67.92; H, 9.49; N, 5.12; S, 11.74.

EXAMPLE 4 The preparation of B, B-bis[3-methyl-4-hydroxy-5-(dimethylaminomethyl)phenylthio diethyl ether.

B, B'-bis(3-methyl-4-hydroxyphenylthio)diethyl ether was prepared byreacting 2-methyl-4-mercaptophenol with B, B'-dichlorodiethyl ether inthe same manner as described in Example 1.

This intermediate was then reacted with formaldehyde and dimethylaminein the same manner as described in Example 1 to yield B,B'-bis[3-methyl-4- hydroxy-S-(di-methylaminomethyl)phenylthio] diethylether as a viscous oil in 90 percent yield.

EXAMPLE 5 The preparation of1,2-bis[2-methyl-3-(dimethylaminomethyl)-4-hydroxy-S-t-butylphenylthio]ethane.

l ,2-bis( 2-methyl-4-hydroxy-5-t-butylphenylthio) ethane, m.p. 142-144C, was prepared by reacting 2- t-butyl-Lmercapto-S-methylphenol withethylene dichloride in the same. manner as described in Example 1.

This intermediate was then reacted with formaldehyde and dimethylaminein the same manner as described in Example 1 to yield1,2-bis[2-methyl-3- (dimethylaminomethyl)-4-hydroxy-5-t-butylphenylthio]ethane, m.p. l48-150 C.

EXAMPLE 6 The preparation of a, a-bis[3-methyl-4-hydroxy-5-(pyrrolidylrnethyl)-phenylthio]-p-diisopropylbenzene.

To a solution of 21 g. (0.15 mole) 2-methyl-4-mercaptophenol and 12 g.(0.075 mole) of p-diisopropenyl benzene in 30 ml. of benzene was added 3g. of KSFO Activated Montmorillonite Catalyst (Girdler Catalyst ChemicalProducts Division of Chernetron Corporation). The mixture was heated toreflux and after a few minutes a solid product precipitated. It wasfiltered off and recrystallized from ethanol, the hot solution beingfiltered to remove the catalyst. The a, ,a'-bis(3-methyl-4-hydroxyphenylthio)-p-diisopropylbenzene obtained had a melting pointof 184-l C.

To a solution of 14.5 g. (0.033 mole)a, a'-bis (3-'methyl-4-hydroxyphenylthio)-p-diisopropylbenzene in 100 ml. of ethanolwas added 4.7 g. (0.066 mole) pyrrolidine and 4.4 g. (0.066 mole) 37percent aqueous formaldehyde. The solution was heated slowly to reflux,then refluxed for two hours- The solution was then cooled and theprecipitate which formed was filtered off, washed with aqueous ethanoland dried yieldin g a, a-bis[3-methyl4-hydroxy-5-(pyrrolidylmethyl)phenylthiol-p-diisopropylbenzene,m.p. l-l 22 C.

EXAMPLE 7 This example demonstrates the usefulness of the compounds ofthis invention as stabilizers for an ethylene propylene terpolymer.

A hexane solution of a commercial ethylenepropylene-dicyclopentadieneterpolymer containing no stabilizer was used as the base polymer. Thesolution was diluted with hexane so as to provide a 4 percent polymersolution. An aliquot portion of a benzene solution of the compound to beevaluated was added so as to provide 1 percent by weight of the additivebased upon the weight of the polymer in the solution. A thin film ofrubber was then deposited on a sodium chloride disk by evaporating fivedrops of the solution on the 1inch diameter disk.

The disks were then placed in a 150 C. oven and removed after 1 hour andevery hour thereafter. At each interval, the infrared spectrum of thepolymer film was obtained. Oxidation of the polymer film is AddedStabilizer Hours to break 1) None 2 (2)bis(3-methyl-4-hydroxyphenylthio)ethane 6 (3)bis(3-t-butyl--hydroxyphenylthio)ethane 8 (4)bisl3-methyl-4-hydroxy-S-(dimethylaminomethyUphenylthiolethane (5)bis[3-t-butyl-4-hydroxy-S-(dimethylaminomethybphenylthiolethane Theresults demonstrate the value of the compounds of this invention (4 and5) as stabilizers compared to compounds representative of the prior art(2 and 3).

Non-discoloring characteristics were determined in this polymer by agingone gram of rubber obtained from the above described polymer solutionsat C.

for 1 hour and observing for color formation.

Added Stabilizer Color (I bis( 3-methyl-4-hydroxyphenylthio) ethaneblack (2) bis( 3-t-butyl-4-hydroxyphenylthio) ethane bluck 3 bisl3-methyl4-hydroxy-5 dimethylaminomethyl )phenylthio1ethane amber (4)bis[ 3-t-butyl-4-hydroxy-5-(dimethylaminomethyl )phenylthiolethane lightamber The results demonstrate the superiority of the compounds of thisinvention (3 and 4) over compounds representative of prior art (1 and 2)in commercially important non-discoloring characteristics.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

l. A chemical of the formula:

no SXSOH (L I l V II: Ra Ra (EH2 NRiRs RiRa wherein R is selected fromthe group consisting of alkyl groups of up to 12 carbon atoms,cycloalkyl groups of from about six to eight carbon atoms and aralkylgroups of from about seven to nine carbon atoms, R and R are selectedfrom the group consisting of hydrogen and methyl, R and R are selectedfrom the group consisting of alkyl groups of up to five carbon atoms,and X is a diradical containing from about two to about 14 carbon. atomsand is selected from the group consisting of:

a. polymethylene diradicals of the formula (CH wherein n is a wholenumber from 2 to 14; b. branched chain polyalkylene diradicals of theformula:

wherein n is a whole number from 0 to 11 and the R groups may behydrogen or alkyl groups and at least one of the R groups is an alkylgroup;

wherein R may be hydrogen or an alkyl group.

2. The compound of claim ll wherein R is methyl, R and R are hydrogen, Rand R are methyl, and X is CH CH 3. The compound of claim ll wherein Ris t-butyl, R and R are hydrogen, R and R are methyl, and X is CH Cl-lmg? mm STATES PATENT We QEYRTEFEQATE @F CRRETEN Patent No. 3,686,313Dated August 22, 19-72 lnventox-(s Francis X. o'shea It is certifiedthat error appears in "the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Cover sheet, item [54], second and third lines and column 1, lines 2 and3, should read: --(DIALKYLAMINOMEITHYL) PHENYLTHIMETHANES.

Columh 8, lines L8- L9; delete wherein R may be hydrogen or an alkylgroup".

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attes'ting Officer Commissionerof Patents

2. The compound of claim 1 wherein R1 is methyl, R2 and R3 are hydrogen,R4 and R5 are methyl, and X is -CH2CH2-.
 3. The compound of claim 1wherein R1 is t-butyl, R2 and R3 are hydrogen, R4 and R5 are methyl, andX is -CH2CH2-.